In a study of the effects of graded concentrations of ambient cigarette smoke on systemic changes in mildly exercised and resting rats, hypothermia was induced only in exercised rats with 15 mg/m3 suspended particulate matter (SPM) and 13 ppm carbon monoxide (CO). Plasma lactic dehydrogenase (PLDH) concentration was elevated after exercise in smoke containing 35 mg/m3 SPM and 51 ppm CO. An increase in concentrations of plasma creatine kinase and blood glucose and in the density of PLDH isoenzyme Band 5 were found in exercised and resting rats at the highest smoke level studied (199 mg/m3 SPM and 220 ppm CO). Plasma corticosterone was elevated only after exercise at the 2 highest smoke levels. The amount of cigarette smoke needed to induce significant systemic changes in rats greatly exceeded acceptable National air quality standards and threshold limits for SPM (National 0.075 mg/m3, American Conference of Governmental Industrial Hygienists, 10 mg/m3) and for CO (National 9 ppm, ACGIH 50 ppm) established for man. BIBLIOGRAPHIC REFERENCES: Altland, P. D.: Altitude and exercise effects on animals: In: Progress in Biometeorology Division B, Progress in Animal Biometeorology Vol. 1, Pt. 2, Chapter 3, pp 124-131, 1963-1973, Ed. H.D. Johnson, Swets and Zeitlinger, Amsterdam, 1976. Rattner, B. A., Ramm, G. M. and Altland, P.D.: Effects of hypoxic exposure on embryonic implantation in mice. Proc. Soc. Exp. Biol. Med. 153: 138-142, 1976.